Digital isolators use transformers or capacitors to magnetically or capacitively couple data across an isolation barrier. Transformers pulse current through a coil to create a small, localized magnetic field that induces current in another coil separated by the isolation barrier, whereas capacitors use low currents to create a coupling electric field across the isolation barrier separating respective capacitor plates. One of the performance parameters for a digital isolator is the isolation capability, which may be measured in terms of the 1 minute withstand voltage (i.e. the voltage that the isolation can withstand for 1 minute before isolation breakdown) or the surge level (i.e. a peak surge voltage that the isolation can withstand instantaneously). Generally, the thicker the isolation barrier can be, combined with a material of higher dielectric constant, the greater the isolation capability that will be obtained. Techniques to obtain thick barriers with high isolation properties are therefore of much use in the fabrication of digital isolators.